Acoustical sound proofing material with improved damping at select frequencies and methods for manufacturing same

ABSTRACT

Panels for use in building construction (partitions, walls, ceilings, floors or doors) which exhibit improved acoustical sound proofing in multiple specific frequency ranges comprise laminated structures having as an integral part thereof one or more layers of viscoelastic material of varied shear moduli which also function as a glue and energy dissipating layer; and, in some embodiments, one or more constraining layers, such as gypsum, cement, metal, cellulose, wood, or petroleum-based products such as plastic, vinyl, plastic or rubber. In one embodiment, standard wallboard, typically gypsum, comprises the external surfaces of the laminated structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 11/772,197 filed Jun. 30, 2007 by Brandon D.Tinianov entitled “Acoustical Sound Proofing Material With ImprovedDamping At Select Frequencies And Methods For Manufacturing Same” whichis incorporated herein by reference in its entirety.

BACKGROUND

Noise control constitutes a rapidly growing economic and public policyconcern for the construction industry. Areas with high acousticalisolation (commonly referred to as ‘soundproofed’) are requested andrequired for a variety of purposes. Apartments, condominiums, hotels,schools and hospitals all require rooms with walls, ceilings and floorsthat reduce the transmission of sound thereby minimizing, oreliminating, the disturbance to people in adjacent rooms. Soundproofingis particularly important in buildings adjacent to publictransportation, such as highways, airports and railroad lines.Additionally theaters, home theaters, music practice rooms, recordingstudios and the like require increased noise abatement. Likewise,hospitals and general healthcare facilities have begun to recognizeacoustical comfort as an important part of a patient's recovery time.One measure of the severity of multi-party residential and commercialnoise control issues is the widespread emergence of model building codesand design guidelines that specify minimum Sound Transmission Class(STC) ratings for specific wall structures within a building. Anothermeasure is the broad emergence of litigation between homeowners andbuilders over the issue of unacceptable noise levels. To the detrimentof the U.S. economy, both problems have resulted in major buildersrefusing to build homes, condos and apartments in certainmunicipalities; and in widespread cancellation of liability insurancefor builders. The International Code Council has established that theminimum sound isolation between multiple tenant dwellings or betweendwellings and corridors is a lab certified STC 50. Regional codes orbuilder specifications for these walls are often STC 60 or more. It isobvious that the problem is compounded when a single wall or structureis value engineered to minimize the material and labor involved duringconstruction.

It is helpful to understand how STC is calculated in order to improvethe performance of building partitions. STC is a single-number ratingthat acts as a weighted average of the noise attenuation (also termedtransmission loss) of a partition across many acoustical frequencies.The STC is derived by fitting a reference rating curve to the soundtransmission loss (TL) values measured for the 16 contiguous one-thirdoctave frequency bands with nominal mid-band frequencies of 125 Hertz(Hz) to 4000 Hertz inclusive, by a standard method. The reference ratingcurve is fitted to the 16 measured TL values such that the sum ofdeficiencies (TL values less than the reference rating curve), does notexceed 32 decibels, and no single deficiency is greater than 8 decibels.The STC value is the numerical value of the reference contour at 500 Hz.For maximum STC rating, it is desirable for the performance of apartition to match the shape of the reference curve and minimize thetotal number of deficiencies.

An example of materials poorly designed for performance according to anSTC-based evaluation is evident in the case of many typical wood framedwall assemblies. A single stud wall assembly with a single layer of typeX gypsum wallboard on each side is recognized as having inadequateacoustical performance. That single stud wall has been laboratory testedto an STC 34—well below building code requirements. A similar wallconfiguration consisting of two layers of type X gypsum wall board onone side and a single layer of type X gypsum board on the other is anSTC 36—only a slightly better result. In both cases, the rating of thewall is limited by poor transmission loss at 125, 160 and 2500 Hz. Inmany cases, the performance is about five to ten decibels lower than itis at other nearby frequencies. For example, at 200 Hz, the wallperforms about 12 decibels better than it does at the adjacentmeasurement frequency, 160 Hz. Similarly, the same assembly performsfive decibels better at 3150 Hz than it does at 2500 Hz.

Additionally, some walls are not designed to perform well with specificregard to an STC curve, but rather to mitigate a specific noise source.A good example is that of home theater noise. With the advent ofmulti-channel sound reproduction systems, and separate low frequencyspeakers (termed ‘subwoofers’) the noise is particularly troublesomebelow 100 Hz. The STC curve does not assess walls or other partitions inthis frequency range. Materials or wall assemblies should be selected toisolate this low frequency sound.

Various construction techniques and products have emerged to address theproblem of noise control, but few are well suited to target thesespecific problem frequencies. Currently available choices include:additional gypsum drywall layers; the addition of resilient channelsplus additional isolated drywall panels and the addition of mass-loadedvinyl barriers plus additional drywall panels; or cellulose-based soundboard. All of these changes incrementally help reduce the noisetransmission, but not to such an extent that identified problemfrequencies would be considered fully mitigated (restoring privacy orcomfort). Each method broadly addresses the problem with additionalmass, isolation, or damping. In other words, each of these is a generalapproach, not a frequency specific one.

More recently, an alternative building noise control product havinglaminated structures utilizing a viscoelastic glue has been introducedto the market. Such structures are disclosed and claimed in U.S. Pat.No. 7,181,891 issued Feb. 27, 2007 to the assignee of the presentapplication. This patent is hereby incorporated by reference herein inits entirety. Laminated structures disclosed and claimed in the '891Patent include gypsum board layers and these laminated structures(sometimes called “panels”) eliminate the need for additional materialssuch as resilient channels, mass loaded vinyl barriers, and additionallayers of drywall during initial construction. The resulting structureimproves acoustical performance over the prior art panels by ten or moredecibels in some cases. However, the described structures are anothergeneral frequency approach. In certain of these structures a singleviscoelastic adhesive (with damping) is incorporated into the laminatedpanel. As will be demonstrated later, such adhesive is designed to dampsound energy within a single frequency band with poorer performance inother sound frequency ranges. For this reason, these structurescompromise performance in certain frequency ranges in an attempt to bestmatch the STC curve.

Accordingly, what is needed is a new material and a new method ofconstruction that allows for the maximum reduction of noise transmissionat low frequencies, high frequencies, or both simultaneously. What isneeded is a panel tuned for performance at multiple problem frequencies.

A figure of merit for the sound attenuating qualities of a material ormethod of construction is the material's Sound Transmission Class (STC).The STC number is a rating which is used in the architectural field torate partitions, doors and windows for their effectiveness in reducingthe transmission of sound. The rating assigned to a particular partitiondesign is a result of acoustical testing and represents a best fit typeof approach to a set of curves that define the sound transmission class.The test is conducted in such a way as to make measurement of thepartition independent of the test environment and gives a number for thepartition performance only. The STC measurement method is defined byASTM E90 “Standard Test Method Laboratory Measurement of Airborne SoundTransmission Loss of Building Partitions and Elements,” and ASTM E413“Classification for Sound Insulation,” used to calculate STC ratingsfrom the sound transmission loss data for a given structure. Thesestandards are available on the Internet at http://www.astm.org.

A second figure of merit is loss factor of the panel. Loss factor is aproperty of a material which is a measure of the amount of damping inthe material. The higher the loss factor, the greater the damping. Theprimary effects of increased panel damping are reduction of vibration atresonance, a more rapid decay of free vibrations, an attenuation ofstructure-borne waves in the panel; and increased sound isolation.

Loss factor is typically given by the Greek symbol “η”. For simplecoating materials, the loss factor may be determined by the ASTM testmethod E756-04 “Standard Test Method for Measuring Vibration-DampingProperties of Materials.” This standard is available on the Internet athttp://www.astm.org. For more complicated structures, such as the onesdescribed in the present invention, a nonstandard test method orcomputer model must be employed to predict or measure the compositematerial loss factor. A loss factor of 0.10 is generally considered aminimum value for significant damping. Compared to this value, mostcommonly used materials, such as wood, steel, ceramic and gypsum, do nothave a high level of damping. For example, steel has a loss factor ofabout 0.001, gypsum wallboard about 0.03, and aluminum a loss factor ofabout 0.006.

In order to design or assess the damping properties of a laminated panelthat uses constrained layer damping, a predictive model is used such asthe well known model first suggested by Ross, Kerwin, and Ungar. TheRoss, Kerwin, and Ungar (RKU) model uses a fourth order differentialequation for a uniform beam with the sandwich construction of the3-layer laminated system represented as an equivalent complex stiffness.

The RKU model is covered in detail in the article “Damping of plateflexural vibrations by means of viscoelastic laminae” by D. Ross, E. E.Ungar, and E. M. Kerwin—Structural Damping, Section IIASME, 1959, NewYork, the content of which article is herein incorporated by reference.The topic is also well covered with specific regard to panels by EricUngar in Chapter 14, “Damping of Panels” in Noise and Vibration Controledited by Leo Beranek, 1971. An extension of this model to systems withmore than three layers has been developed by David Jones in section 8.3of his book Viscoelastic Vibration Damping. This model is used in all ofthe predictive calculations used for the present invention.

SUMMARY OF THE INVENTION

In accordance with the present invention, a new laminated structure andassociated manufacturing process are disclosed which significantlyimproves the ability of a wall, ceiling, floor or door to resist thetransmission of noise from one room to an adjacent room, or from theexterior to the interior of a room, or from the interior to the exteriorof a room at both low frequencies and high frequencies.

In one embodiment the structure comprises a lamination of severaldifferent materials. In accordance with one embodiment, a laminatedsubstitute for drywall comprises a first layer of selected thicknessgypsum board which is glued to a center constraining material, such as32 gauge sheet steel. The first adhesive has a shear modulus designed toachieve maximum damping at a target frequency such as 160 Hz. On thesecond surface of the steel constraining layer, a second layer ofselected thickness gypsum board is glued in place using a secondadhesive layer. The second adhesive layer has a different shear modulusto achieve maximum damping at a different frequency such as 2500 Hz. Inone embodiment, the glue layers are two versions of a speciallyformulated QuietGlue® adhesive, which is a viscoelastic materialavailable from Serious Materials, 1250 Elko Drive, Sunnyvale, Calif.94089. In addition to the typical chemicals that make up the QuietGlue®adhesive, additional plasticizing compounds are added to aid the shiftof the shear modulus to achieve maximum damping at a different frequencywhile keeping other adhesive material properties constant.

Formed on the interior surfaces of the two gypsum boards, the glue layeris about 1/16 inch thick. In one instance, a 4 foot×8 foot panelconsisting of two ¼ inch thick gypsum wall board panels laminated over a30 gauge steel sheet using two 1/16 inch thick layers of glue has atotal thickness of approximately ⅝ inch. When used on both sides of astandard single wood stud frame, the assembly has an STC value ofapproximately 54. For comparison, a similar wall assembly constructedwith ½ inch thick standard gypsum wallboard has an STC rating ofapproximately 34. The result is a reduction in noise transmitted throughthe wall structure of approximately 20 decibels compared to the samestructure using common (untreated) gypsum boards of equivalent mass andthickness, and construction effort.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will be more fully understood in light of the followingdrawings taken together with the following detailed description inwhich:

FIG. 1 shows an embodiment of a laminated structure fabricated inaccordance with this invention for minimizing the transmission of soundthrough the material.

FIG. 2 shows another embodiment of a laminated structure fabricated inaccordance with this invention for minimizing the transmission of soundthrough the material.

FIG. 3 shows another embodiment of a laminated structure fabricated inaccordance with this invention for minimizing the transmission of soundthrough the material.

FIG. 4 shows the computed loss factor associated with several laminatedpanels, each with a single glue formulation.

FIG. 5 shows the computed loss factor associated with several laminatedpanels, each with a single glue formulation and the computed loss factorassociated with a dual glue embodiment of the present invention.

FIG. 6A is a plan view of a wall structure wherein one panel of the wallstructure 600 comprises a laminated panel constructed in accordance withan embodiment of the present invention.

FIG. 6B is a cross sectional view taken along lines 6B-6B in FIG. 6.

FIG. 7A is a plan view of a wall structure wherein two panels of thewall structure 700 include laminated panels constructed in accordancewith the present invention.

FIG. 7B is a cross view taken along lines 7B-7B in FIG. 7A.

DESCRIPTION OF SOME EMBODIMENTS

The following detailed description is meant to be exemplary only and notlimiting. Other embodiments of this invention, such as the number, type,thickness, dimensions, area, shape, and placement order of both externaland internal layer materials, will be obvious to those skilled in theart in view of this description.

The process for creating laminated panels in accordance with the presentinvention takes into account many factors: exact chemical composition ofthe glue; pressing process; and drying and dehumidification process.

FIG. 1 shows laminated structure 100 according to one embodiment of thepresent invention. In FIG. 1, the layers in the structure are describedfrom top to bottom with the structure oriented horizontally as shown. Itshould be understood, however, that the laminated structure of thisinvention will be oriented vertically when placed on vertical walls anddoors, as well as horizontally or even at an angle when placed onceilings and floors. Therefore, the reference to top and bottom layersis to be understood to refer only to these layers as oriented in FIG. 1and not in the context of the vertical or other use of this structure.In FIG. 1, reference character 100 refers to the entire laminated panel.A top layer 101 is made up of a standard gypsum material and in oneembodiment is ¼ inch thick. Of course, many other combinations andthicknesses can be used for any of the layers as desired. Thethicknesses are limited only by the acoustical attenuation (i.e., STCrating) desired for the resulting laminated structure and by the weightof the resulting structure which will limit the ability of workers toinstall the laminated panels on walls, ceilings, floors and doors forits intended use.

The gypsum board in top layer 101 typically is fabricated using standardwell-known techniques and thus the method for fabricating the gypsumboard will not be described. Alternately, layer 101 may be any one of alayer of cement-based board, wood, magnesium oxide-based board orcalcium silicate board. Next, on the bottom surface 101-1 of the gypsumboard 101 is a patterned layer of glue 104 called “QuietGlue®” adhesive.Glue 104, made of a viscoelastic polymer modified with additives to giveit a prescribed shear modulus upon curing, optimizes the sounddissipation at a specific range of frequencies. Glue layer 104 may havea thickness from about 1/64 inch to about ⅛ inch although otherthicknesses may be used. When energy in sound interacts with the gluewhich is constrained by surrounding layers, the sound energy will besignificantly dissipated thereby reducing the sound's amplitude across atarget frequency range. As a result, the sound energy which willtransmit through the resulting laminated structure is significantlyreduced. Typically, glue 104 is made of the materials as set forth inTABLE 1, although other glues having similar characteristics to thoseset forth directly below in Table 1 can also be used in this invention.

An important characteristic of the glue composition and the overalllaminated structure is the shear modulus of the glue when cured. Theshear modulus can be modified from 10³ to 10⁷ N/m² (or Pascals)depending on the frequency range of interest with the given materials ofthe given ranges listed in Table 1.

TABLE 1 QuietGlue ® Adhesive Chemical Makeup WEIGHT % Shear Shear ShearModulus Modulus Modulus 10³ Pa 10⁵ Pa 10⁶ Pa COMPONENTS Min MaxPreferred (ex. 160 Hz) (ex. 2500 Hz) (ex. 5500 Hz) acrylate polymer30.00% 70.00% Shear   60%   40%   30% Modulus Dependant ethyl acrylate,0.05% 3.00% 0.37% 0.37% 0.37% 0.37% methacrylic acid, polymer withethyl-2- propenoate hydrophobic 0.00% 0.50% 0.21% 0.21% 0.21% 0.21%silica paraffin oil 0.10% 4.00% 1.95% 1.95% 1.95% 1.95% Silicon dioxide0.00% 0.30% 0.13% 0.13% 0.13% 0.13% Sodium 0.01% 1.50% 0.66% 0.66% 0.66%0.66% carbonate Stearic acid, 0.00% 0.30% 0.13% 0.13% 0.13% 0.13%aluminum salt surfactant 0.00% 1.00% 0.55% 0.55% 0.55% 0.55% rosin ester1.00% 9.00% 4.96% 4.93% 4.93% 4.93% water 25.00% 40.00% 30.90% 30.90% 30.90%  30.90%  2-Pyridinethiol, 0.00% 0.30% 0.17% 0.17% 0.17% 0.17%1-oxide, sodium salt High Tg (>0 C.) 0.00% 30.00% Shear   0%   20%   30%acrylic polymer modulus or latex, particle dependant size <0.35 uM

Note that as shown in Table 1, the sound frequency which is bestattenuated by the glue varies from approximately 160 Hz for a shearmodulus of about 103 Pascals (Pa), to approximately 2500 Hz for a shearmodulus of about 105 Pa, and to approximately 5500 Hz for a shearmodulus of about 106 Pa. The shear modulus is increased by decreasingthe percent by weight of acrylate polymer and increasing the percent byweight of acrylic polymer or latex, all other ingredients remainingconstant, as shown in Table 1.

Table 1 shows in the fourth column a preferred embodiment of theviscoelastic glue which has an optimum sound attenuation at 160 Hz. Thepreferred formulation is but one example of a viscoelastic glue. Otherformulations may be used to achieve similar results and the range givenis an example of successful formulations investigated here.

The physical solid-state characteristics of QuietGlue® adhesive include:

-   -   1) a broad glass transition temperature below room temperature;    -   2) mechanical response typical of a rubber (i.e., elongation at        break, low elastic modulus);    -   3) strong peel strength at room temperature;    -   4) shear modulus between 10³ and 10⁷ N/m² at room temperature;    -   6) does not dissolve in water (swells poorly);    -   7) peels off the substrate easily at temperature of dry ice; and        QuietGlue® adhesive may be obtained from Serious Materials, 1250        Elko Drive, Sunnyvale, Calif. 94089.

Applied to glue layer 104 is a constraining layer 102 made up of gypsum,vinyl, steel, wood, cement or another material suitable for theapplication. If layer 102 is vinyl, the vinyl is mass loaded and, in oneembodiment, has a surface density of one pound per square foot orgreater. Mass loaded vinyl is available from a number of manufacturers,including Technifoam, of Minneapolis, Minn. The constraining layer 102may improve the sound attenuation and physical characteristics of alaminated panel so constructed.

As a further example, constraining layer 102 can be galvanized steel ofa thickness such as 30 gauge (0.012 inch thick). Steel has a higherYoung's Modulus than vinyl and thus can outperform vinyl as an acousticconstraining layer. However, for other ease-of-cutting reasons, vinylcan be used in the laminated structure in place of steel. Cellulose,wood, plastic, cement or other constraining materials may also be usedin place of vinyl or metal. The alternate material can be any type andany appropriate thickness. In the example of FIG. 1, the constrainingmaterial 102 approximates the size and shape of the glue layers 104 towhich it is applied and to the upper panel 101.

A second layer of viscoelastic glue 105 is applied to the second surfaceof constraining layer 102. Glue 105 is similar to glue 104 in all waysexcept for the shear modulus of glue 105 in the cured state. As withglue 104, a prescribed shear modulus allows for optimization of thesound dissipation at a specific range of frequencies. By setting theshear modulus (and therefore target frequency) of glue 105 differentfrom the shear modulus (and therefore the target frequency) of gluelayer 104, the laminated panel is able to dissipate two frequencyregions simultaneously and improve the overall acoustical attenuation ofthe panel. By adding one or more additional constraining layers and therequired one or more additional glue layers, the laminated panel can betuned to attenuate three or more target frequency ranges.

Gypsum board layer 103 is placed on the bottom of the structure andcarefully pressed in a controlled manner with respect to uniformpressure (measured in pounds per square inch), temperature and time.Alternately, layer 103 may be any one of a layer of cement-based board,wood, magnesium oxide-based board or calcium silicate board.

Finally, the assembly is subjected to dehumidification and drying toallow the panels to dry, typically for forty-eight (48) hours.

In one embodiment of this invention, the glue 104, when spread over thebottom surface 101-1 of top layer 101 or of any other material, issubject to a gas flow for about forty-five seconds to partially dry theglue. The gas can be heated, in which case the flow time may be reduced.The glue 104, when originally spread out over any material to which itis being applied, is liquid. By partially drying out the glue 104,either by air drying for a selected time or by providing a gas flow overthe surface of the glue, the glue 104 becomes a sticky paste much likethe glue on a tape, commonly termed a pressure sensitive adhesive(“PSA”). The gas flowing over the glue 104 can be, for example, air ordry nitrogen. The gas dehumidifies the glue 104, improving manufacturingthroughput compared to the pressing process described for example, inU.S. Pat. No. 7,181,891 wherein the glue 104 would not be dried for anappreciable time prior to placing layer 103 in place.

The second panel, for example the constraining layer 102, is then placedover the glue 104 and pressed against the material beneath the glue 104(as in the example of FIG. 1, top layer 101) for a selected time at aselected pressure.

A second layer of glue 105 is applied to the surface of the constrainingmaterial 102 on the side of constraining material 102 that is facingaway from the top layer 101. In one embodiment, glue layer 105 isapplied to the interior side of bottom layer 103 instead of beingapplied to layer 102. A gas can be flowed or forced over glue layer 105to change glue 105 into PSA, if desired. Bottom layer 103 is placed overthe stack of layers 101, 104, 102 and 105. The resulting structure isallowed to set under a pressure of approximately two to five pounds persquare inch, depending on the exact requirements of each assembly, for atime which can range from minutes up to hours, depending on the state ofglue layers 104 and 105 in the final assembly. Other pressures may beused as desired.

In one embodiment the glue layers 104 and 105 are about 1/16^(th) of aninch thick; however other thicknesses may be used. The glue layers 104and 105 may be applied with a brush, putty knife, caulking gun, sprayedon, applied using glue tape or well known other means.

FIG. 2 shows a second embodiment of this invention involving a laminatedpanel 200 in which there is no constraining layer. In FIG. 2, a toplayer 101 is made up of standard gypsum material and in one embodimentis 5/16 inch thick. Next, on the bottom surface 201-1 of the gypsumboard 201 is a patterned layer of viscoelastic glue 204 called“QuietGlue®” adhesive. The pattern of glue 204 coverage may constituteanywhere from twenty (20) to eighty (80) percent of the surface area201-1 of gypsum board 201. A second layer of glue 205 is also placed onthe bottom surface 201-1 of gypsum board 201. Glue 205 also has apattern covering from twenty (20) to eighty (80) percent of surface201-1 and is placed so that it does not materially or substantiallyoverlap glue 204 anywhere on surface 201-1. Glue layers 204 and 205 arephysically similar in many ways except for their shear moduli. As withassembly 100, the glues 204 and 205 are designed with different shearmoduli to dissipate energy at different frequency ranges. The bottomlayer of material 203 is placed over the stack of layers 201, 204 and205. The resulting structure is allowed to set for a selected time undera pressure of approximately two to five pounds per square inch,depending on the exact requirements of each assembly, although otherpressures may be used as desired. The set time under pressure can varyfrom minutes to hours as described above depending on the state of glues204 and 205 at the time panel 203 is joined to the assembly.

In fabricating the structure of FIG. 2, the assembly method can besimilar to that described for the structure of FIG. 1. In one embodimentof FIG.2, exterior layers 201 and 203 are gypsum board each having athickness of 5/16 inch.

FIG. 3 is an example of a third laminated panel 300 in which a secondconstraining layer 306 and a third glue layer 307 are added to theassembly shown in FIG. 1. Exterior layers 301 and 303 are in oneembodiment gypsum board having a thickness of ¼ inch. In fabricatinglaminated structure 300 of FIG. 3, the method is similar to thatdescribed for laminated structures 100 and 200 of FIG. 1 and FIG. 2,respectfully. However, before the bottom layer 303 is applied (bottomlayer 303 corresponds to bottom layers 103 and 203 in FIGS. 1 and 2,respectfully) a first constraining material 302 is placed over glue 304.Next, a second layer of glue 305 is applied to the surface of theconstraining material on the side of the constraining material that isfacing away from the top layer 301. An additional constraining layer 306and glue layer 307 are placed on the assembly before the final layer 303is added. In one embodiment the glue layer 305 is applied to the exposedside of the second constraining layer 306. In another embodiment gluelayer 307 is applied to the interior side of the bottom layer 303instead of being applied to constraining layer 306. Suitable materialsfor constraining layers 302 and 306 are the same as those identifiedabove for constraining layer 102. The bottom layer 303 is placed overthe stack of layers 301, 304, 302, 305, 306, and 307. Laminatedstructure 300 is dried in a prescribed manner under a pressure ofapproximately two to five pounds per square inch, depending on the exactrequirements of each assembly, although other pressures may be used asdesired. Drying is typically performed by heating for a time from about24 to about 48 hours and at a temperature in the range of from about 90°F. to about 120° F. Drying time for the final assembly can be reduced toas little as minutes by flowing, blowing or forcing air or otherappropriate gas past each layer of glue to remove liquid such as waterfrom each layer of glue and thus convert the glue into PSA.

FIG. 4 shows the calculated loss factors for the embodiment shown inFIG. 1 where both glue layers 104 and 105 have the same given shearmodulus. Nine total curves are shown representing glue shear moduli from10³ Pascals (Pa) to 10⁷ Pa. A Pascal is a Newton of force per squaremeter. Curve 401 represents the calculated panel loss factor forlaminated panel 100 with glue 104 and glue 105 having a shear modulus5×10⁴ Pa. Panel 100 has a maximum loss factor of approximately 0.25 atabout 1500 Hz. Curve 402 represents the calculated panel loss factor forlaminated panel 100 with glues 104 and 105 having a shear modulus 1×10⁶Pa. Curve 402 shows a maximum loss factor of approximately 0.25 acrossthe frequency range of 6000 Hz to 10,000 Hz. Curve 403 represents thecalculated panel loss factor for laminated panel 100 with glues 104 and105 having a shear modulus 1×10⁷ Pa. Curve 403 shows a maximum lossfactor of approximately 0.14 from 10,000 Hz and above.

FIG. 5 shows the calculated loss factor for the embodiment shown in FIG.1 where glue layers 104 and 105 have different given shear moduli. Curve504 represents the predicted loss factor for a panel such as anembodiment shown in FIG. 1 where glue 104 has a shear modulus of 10³ Paand glue 105 has a shear modulus of 10⁶ Pa. As shown by curve 504, thepanel 100 with two different glues 104, 105 as described, has a maximumloss factor of 0.25 at around 100 Hz and a loss factor above 0.1 fromabout 4600 Hz to 10,000 Hz. Curves 501, 502, and 503 (duplicates ofcurves 401, 402, and 403 respectively in FIG. 4) are shown forcomparison of the predicted loss factor associated with panel 100 withtwo different glues to the predicted loss factor associated with panel100 with glue layers 104 and 105 having the same shear modulus. It canbe seen that the composite performance exceeds that of any othersingle-glue-formulation-based panel over many, if not all frequencies.Such a dual formula glued panel can address the low and high frequencyproblems evident in today's typical wall assemblies.

It is important to note that the viscoelastic adhesive materialproperties also vary tremendously as a function of temperature much liketheir dependence on frequency. For example, for a given viscoelasticmaterial, the modulus and loss factor might be the same at 10 Hz and 25degrees C. as it is at 700 Hz and 50 degrees C. Viscoelastic materialsbehave “colder” at high frequencies and “warmer” at low frequencies. Inother words, there is a direct and proportional relationship betweentemperature and frequency. In fact, there are several ways todemonstrate the properties of a given viscoelastic material. Thetemperature could be held constant and the material tested over a verywide frequency range. Or, the temperature could be varied and thematerial tested over a much narrower frequency range. Then,temperature/frequency equivalence is applied to finally “reduce” thedata and characterize the material. This phenomenon is reviewed in DavidJones' book Viscoelastic Vibration Damping, the content of which isherein incorporated by reference.

For these reasons, the present invention may also be considered usefulfor providing improved acoustical isolation for assemblies subject tomultiple temperature exposures. In such a case, a first layer of gluecould be designed to have maximum damping at 0 degrees C. (probablewinter temperatures in a cold climate) and a second layer of gluedesigned to have maximum damping at 25 degrees C. (probable summertemperatures) in the same panel.

Referring to FIGS. 6A and 6B, wall assembly 600 is shown. This assemblyincludes a front side 610 which is constructed using a material such aslaminated structure 100 disclosed in FIG. 1, and a rear panel 608 whichis a single layer of type X gypsum wallboard. Panels 608 and 610 areattached to 2×4 studs 602, 604 and 606. These will be better appreciatedby reference to the cross sectional view of FIG. 6B. Batt-type orblown-in thermal insulation 612 is located in each of cavities 618 and620 which are enclosed between the 2×4 stud structures.

Referring to FIGS. 7A and 7B, wall panel 700 has a front side 710 andback side 708 each using a laminated structure of one quarter inchgypsum board constructed using the laminated structure 100 shown inFIG. 1. As disclosed similarly with regard to FIGS. 6A and 6B, the wallpanel assembly 700 includes 2×4 stud structures 702, 704 and 706. In afashion similar to that shown in FIG. 6B, cavities 718 and 720 includebatt-type or equivalent insulation 712. Since wall panel assembly 700includes laminated front and rear panels, an increased soundtransmission class rating is provided and similarly additional fireresistance is also provided.

The dimensions given for each material in the laminated structures ofthe present invention can be varied in view of cost, overall thickness,weight, and desired sound transmission properties. For example, two ormore non-overlapping patterns of glue with different shear moduli can beused in the embodiment of FIG. 2 to achieve peak sound attenuation overtwo or more different frequency ranges. Similarly each layer of glueshown in each of the embodiments of FIGS. 1 and 3 can similarly be madeup of two or more patterned glues, each glue having a different andunique shear modulus to provide a panel which achieves peak soundattenuation over as many different frequency ranges as there aredifferent types of glue.

An embodiment of this invention uses two or more glues with differentshear moduli in each glue layer in the structure of FIG. 1 or thestructure of FIG. 3. Each glue layer can be arranged so that glues withidentical shear moduli are directly above or below each other in thedifferent glue layers. Alternatively each glue layer can be arranged sothat glues with identical shear moduli are not directly above or beloweach other in these structures.

As will be apparent from the above description, the structures of thatpattern can be tailored to give desired sound attenuation in selectedfrequency ranges.

The patterns of glue making up each glue layer can be applied in stripsor squares or other shapes using brushes or glue applicators ofwell-known design.

The above-described embodiments and their dimensions are illustrativeand not limiting. In addition, further other embodiments of thisinvention will be obvious in view of the above description.

Accordingly, the laminated structure of this invention provides asignificant improvement in the sound transmission class numberassociated with the structures and thus reduces significantly the soundtransmitted from one room to adjacent rooms while simultaneouslyproviding specific additional sound dissipation at multiple frequencies.

Other embodiments of this invention will be obvious in view of the abovedescription.

1. A laminated panel comprising: a first layer of material having anexternal surface and an internal surface; a second layer of materialhaving an external surface and an internal surface; and a layer of gluein contact with the internal surface of said first layer of material andwith the internal surface of said second layer of material, thereby tobond together the first layer of material and the second layer ofmaterial, said layer of glue being made up of at least two differentglues, including a first glue having a first shear modulus and a secondglue having a second shear modulus.
 2. The panel of claim 1 wherein saidfirst glue is formed in a first pattern and said second glue is formedin a second pattern such that said first glue does not materiallyoverlap said second glue.
 3. The panel of claim 2 wherein said firstshear modulus results in said first glue having a first loss factorwhich is most effective in a first frequency range and said second shearmodulus results in said second glue having a second loss factor which ismost effective in a second frequency range.
 4. The panel of claim 3wherein said first frequency range and said second frequency rangediffer from each other.
 5. The panel of claim 3 wherein the frequency atwhich said first loss factor peaks in said first frequency range differsfrom the frequency at which said second loss factor peaks in said secondfrequency range.
 6. The panel of claim 3 wherein the frequency at whichsaid first loss factor peaks in said first frequency range differs fromthe frequency at which said second loss factor peaks in said secondfrequency range in such a manner that the first glue attenuates acousticenergy in a relatively low frequency range and the second glueattenuates acoustic energy in a relatively high frequency range.
 7. Thepanel of claim 6 wherein said acoustic energy comprises sound andvibration energy.
 8. The panel of claim 7 wherein said acoustic energycomprises airborne sound and structural vibration energy.
 9. The panelof claim 1 further comprising: a third layer of material having anexternal surface and an internal surface; and a second layer of glue incontact with the external surface of said second layer of material andthe internal surface of said third layer of material, thereby to bondsaid third layer of material to said second layer of material.
 10. Thepanel of claim 9 wherein said second layer of glue has a unique shearmodulus different from the shear moduli of said first glue and saidsecond glue thereby to provide to said third layer of glue a peak lossfactor in a third frequency range.
 11. The panel of claim 9 wherein saidsecond layer of glue is made up of at least two different glues, a thirdglue and a fourth glue, said third glue having a third shear modulus andsaid fourth glue having a fourth shear modulus.
 12. The panel of claim 9wherein said third glue is formed in a first pattern and said fourthglue is formed in a second pattern such that said third glue does notmaterially overlap said fourth glue.
 13. The panel of claim 12 whereinsaid third shear modulus results in said third glue having a third lossfactor which is most effective in a third frequency range and saidfourth shear modulus results in said fourth glue having a fourth lossfactor which is most effective in a fourth frequency range.
 14. Thepanel of claim 12 wherein said third frequency range and said fourthfrequency range differ from each other.
 15. The panel of claim 12wherein the frequency at which said third loss factor peaks in saidthird frequency range differs from the frequency at which said fourthloss factor peaks in said fourth frequency range.
 16. The panel of claim12 wherein the frequency at which said third loss factor peaks in saidthird frequency range differs from the frequency at which said fourthloss factor peaks in said fourth frequency range in such a manner thatthe third glue attenuates acoustic energy in a relatively low frequencyrange and the fourth glue attenuates acoustic energy in a relativelyhigh frequency range.
 17. The panel of claim 16 wherein said acousticenergy comprises sound and vibration energy.
 18. The panel of claim 17wherein said acoustic energy comprises airborne sound and structuralvibration energy.
 19. A laminated panel comprising: three or more layersof material, two of said three or more layers of material each having anexternal surface and an internal surface and the third layer of materialand any additional layers of material having only internal surfaces; thethird layer of material comprises a constraining layer of materialbetween the internal surfaces of two of said three or more layers ofmaterial; and at least two layers of glue, each layer of glue being incontact with the internal surfaces of at least two layers of materials,each layer of glue bonding together the two layers of material withwhich the layer of glue is in contact, and at least one of said twolayers of glue having a different shear modulus from the shear moduli ofthe other or others of said at least two layers of glue.
 20. Thelaminated panel of claim 19 wherein at least one of said two layers ofglue comprises at least two different glues, including a first gluehaving a first shear modulus and a second glue having a second shearmodulus.
 21. The panel of claim 19 wherein at least one of said twolayers of glue comprises a first glue formed in a first pattern and asecond glue formed in a second pattern such that said first glue doesnot materially overlap said second glue.
 22. The panel of claim 19wherein said first shear modulus results in said first glue having afirst loss factor which is most effective in a first frequency range andsaid second shear modulus results in said second glue having a secondloss factor which is most effective in a second frequency range.
 23. Thepanel of claim 22 wherein said first frequency range and said secondfrequency range differ from each other.
 24. The panel of claim 22wherein the frequency at which said first loss factor peaks in saidfirst frequency range differs from the frequency at which said secondloss factor peaks in said second frequency range.
 25. The panel of claim22 wherein the frequency at which said first loss factor peaks in saidfirst frequency range differs from the frequency at which said secondloss factor peaks in said second frequency range in such a manner thatthe first glue attenuates acoustic energy in a relatively low frequencyrange and the second glue attenuates acoustic energy in a relativelyhigh frequency range.
 26. The panel of claim 25 wherein said acousticenergy comprises sound and vibration energy.
 27. The panel of claim 26wherein said acoustic energy comprises airborne sound and structuralvibration energy.
 28. A method of forming a laminated panel, said methodcomprising: forming a first layer of material having an external surfaceand an internal surface; forming a second layer of material having anexternal surface and an internal surface; and placing a layer of glue incontact with the internal surface of said first layer of material andwith the internal surface of said second layer of material, thereby tobond together the first layer of material and the second layer ofmaterial, said layer of glue being made up of at least two differentglues, including a first glue having a first shear modulus and a secondglue having a second shear modulus.
 29. The method of claim 28 whereinsaid first glue is formed in a first pattern and said second glue isformed in a second pattern such that said first glue does not materiallyoverlap said second glue.
 30. The method of claim 29 wherein said firstshear modulus results in said first glue having a first loss factorwhich is most effective in a first frequency range and said second shearmodulus results in said second glue having a second loss factor which ismost effective in a second frequency range.
 31. The method of claim 30wherein said first frequency range and said second frequency rangediffer from each other.
 32. The method of claim 31 wherein the frequencyat which said first loss factor peaks in said first frequency rangediffers from the frequency at which said second loss factor peaks insaid second frequency range.
 33. The method of claim 31 wherein thefrequency at which said first loss factor peaks in said first frequencyrange differs from the frequency at which said second loss factor peaksin said second frequency range in such a manner that the first glueattenuates acoustic energy in a relatively low frequency range and thesecond glue attenuates acoustic energy in a relatively high frequencyrange.
 34. The method of claim 33 wherein said acoustic energy comprisessound and vibration energy.
 35. The method of claim 34 wherein saidacoustic energy comprises airborne sound and structural vibrationenergy.
 36. The method of claim 28 further comprising: forming a thirdlayer of material having an external surface and an internal surface;and placing a second layer of glue in contact with the external surfaceof said second layer of material and the internal surface of said thirdlayer of material, thereby to bond said third layer of material to saidsecond layer of material.
 37. The method of claim 36 wherein said secondlayer of glue has a unique shear modulus different from the shear moduliof said first glue and said second glue thereby to provide to saidsecond layer of glue a peak loss factor in a third frequency range. 38.The method of claim 36 wherein said second layer of glue is made up ofat least two different glues, a third glue and a fourth glue, said thirdglue having a third shear modulus and said fourth glue having a fourthshear modulus.
 39. The method of claim 38 wherein said third glue isformed in a first pattern and said fourth glue is formed in a secondpattern such that said third glue does not materially overlap saidfourth glue.
 40. The method of claim 38 wherein said third shear modulusresults in said third glue having a third loss factor which is mosteffective in a third frequency range and said fourth shear modulusresults in said fourth glue having a fourth loss factor which is mosteffective in a fourth frequency range.
 41. The method of claim 38wherein said third frequency range and said fourth frequency rangediffer from each other.
 42. The method of claim 38 wherein the frequencyat which said third loss factor peaks in said third frequency rangediffers from the frequency at which said fourth loss factor peaks insaid fourth frequency range.
 43. The method of claim 38 wherein thefrequency at which said third loss factor peaks in said third frequencyrange differs from the frequency at which said fourth loss factor peaksin said fourth frequency range in such a manner that the third glueattenuates acoustic energy in a relatively low frequency range and thefourth glue attenuates acoustic energy in a relatively high frequencyrange.
 44. The method of claim 43 wherein said acoustic energy comprisessound and vibration energy.
 45. The method of claim 44 wherein saidacoustic energy comprises airborne sound and structural vibrationenergy.